Cast iron and the method of making same



Patented Sept. 4, 1928.

1,683,086 PATENT OFFICE.

AUGUSTUS I. MEEHAN, OFL UHATTANOOGA, TENNESSEE.

CAST IRON AND THE METHOD OF MAKING SAME.

No Drawing.

The present invention relates to the treatment of metals, and, moreparticularly, to the treatment of molten metal in the manufacture ofcastings.

An object of the invention is to provide a process for the manufactureof castings of special strength and uniformity, such as will insure thequality sought in the finished castings.

l-Ieretofore, been the practice in when deemed essential, it has themanufacture of grey iron castings to add to the molten metal a suitableagent in order to obtain the carbon in the desired forms.

In the breaking down of the iron carbide in the metal duringsolidification, ferro-silicon generally has been used as a graphitizingagent in order to provide the proper ratio of combined and graphiticcarbon in the casting, and in a treatment of molten metal such as wouldupon solidification produce a castin g white in fracture, into metal forcastings the fracture of which would be grey, the use of the silicidesubstantially free from iron is suggested in my Patent 1,499,068,granted June 24th, 1924.

My investigations have disclosed that the character of gray castings maybe materially improved by the treatment of molten metal already suitablefor making the same, through the introduction in the molten metal of asilicide substantially free from iron. It has been found that a silicideof an alkaline earth metal, such as calcium or magnesium, or otheralkaline earth metal, will materially improve the casting, even thoughit contains an amount of graphitic carbon that was not precipitated bythe silicide referred to, and would have been gray in fracture withoutthe introduction of the silicide.

The introduction of such a silicide, even in molten metal which whencast ordinarily would be gray in character, is readily soluble andworkable, and acts to precipitate additional carbon in spite of whichthe tensile and transverse strength will be materially increased. It hasbeen found that the silicide produces this effect in molten iron adaptedto produce a casting containing approximately 3% of combined carbon, andeven in iron containing less than 1% of combined carbon.

By the statement that the silicide is substantially free from iron, ismeant that the iron content of the treating agent or alloy is relativelyinconsiderable.

I have also found that in the production of Application filed June 16,1927. Serial No. 189,419.

castings, the silicide agent may be accompanied to advantage by a secondalkaline earth metal, such as magnesium, strontium, barium, etc. Forexample, an alloy agent of calcium, silicon and an inconsiderable amountof iron may also include to advantage either magnesium or strontium orbarium, etc.

The agents described above, when used separately or combined as alloys,have been found to be of increased or intensified value if accompaniedby nickel, or aluminum, or chromium, or titanium or vanadium.

The following alloys are given as examples of ones that have been foundto be satisfactory:

Example 1.

These agents may be introduced into the molten metal, in any suitablemanner, either in combination, i. e., as alloys, or separately.Ordinarily the alloy or separate elements are reduced to relativelysmall particles, although the alloy may be used in brick or briquetteform, and a few ounces of the same used to a small percentage of themetal treated. ,The agents may be added in the spout as the molten metalruns from the furnace, or thrown into the stream of metal where itenters the ladle from the spout, or else added to the metal in thefurnace.

A Per cent. Calcium 33 to 35 Silicon 62 to 65 Iron 3 Example 1 Per cent.Calclum 33 Aluminum n 8 Iron 3 Silicon J 56 Example 3.

Per cent. Silicon 53 Calcium H 32.60 Nickel 3. 60 Iron 2.60

Example 1,.

Per cent. Calcium 35 Magnesium 9 Silicon 56 Example 5.

Per cent. S1l1con 51 Nickel 5 Magnesium 9 vCalcium 35 Although thepercentages given in the foregoing examples may be varied considerably,it is J be understood that Where reference is made in the specificationand claims to the use of a silicide, such as calcium or I mean an amountof the same sufficient to produce an appreciable graphitizing effect.Since the molten iron will vary in its-characteristics, the amount ofsilicide needed, in particular instances, will be governed accordingly,the silicide being used, of course, in sufficient amounts to pro ducethe desired graphitizing effect.

By molten white iron, I mean such molten iron as will produce castingssubstantially free from graphitic carbon. By white iron I mean suchcastings as are substantially free from graphitic carbon. By gray molteniron I means such molten iron as will produce castings in which more orless graphitic carbon will be present. By gray iron I mean castings inwhich more or less graphite is present.

claim:

1. That improvement in the art of making east-iron which consists inadding to gray molten metal a silicide containing an alkaline earthmetal, and another graphitizing agent such as nickel.

2. That improvement in the art of making cast-iron which consists inadding to molten metal a silicide containing an alkaline earth metal,and another graphitizing agent such as nickel, and a second alkalineearth metal.

3. That improvement in the art of making magnesium silicide,

cast-iron which consists in adding to molten iron calcium silicide, agraphitizing agent such as nickel, and a second alkaline earth metal.

4. That improvement in the art of making castings which consists inadding to may molten iron, a silicide substantially free rom iron in anamount sufficient to produce a graphitizing effect.

5. That improvement in the art of making castings which consists inadding to gray molten iron, calcium silicide in' an amount sufficient toproduce a graphitizing effect.

6'. Thatimprovement in the art of making castings which consists inadding to gray molten iron, a silicide substantially free from iron inan amount sufficient to produce a graphitizing effect, and anothergraphitizing agent.

7. That improvement in the art of making castings which consists inadding to gray molten iron, a silicide substantially free from iron. inan amount sufficient to produce a graphitizing effect, and anothergraphitizing agent in the form of an alkaline earth metal.

8. That improvement in the art of making castings which consists inadding to gray molten iron, calcium silicide in an amount sufficient toproduce a graphitizing effect and another graphitizing agent in the formof an alkaline earth metal.

In testimony whereof I have hereunto set my hand.

AUGUSTUS F. MEEHAN.

